The biggest issue with Painter is whether they can resist the temptation to rush him.
I think he needs to start next year in AA, then force a promotion to AAA, but give him time to work on his secondary pitches - no matter how dominant he is in the minors with his FB, to be successful as a starter at the ML level he has to have 3 pitches he can throw for strikes.
I think one thing that leads to young pitchers getting injured is rushing them before they trust their secondary pitches, so their response to adversity is to "throw harder" not smarter - and that's how you put undo stress on your arm.